JPWO2013157488A1 - Fuel cell system - Google Patents

Abstract

A turbo-type oxidant pump (21) that has a rotary shaft supported by an air bearing and takes in an oxidant gas by rotational movement and sends it to the fuel cell (10); and an actual flow rate detection means (Q) for the oxidant gas; The pressure adjusting means (24) for the oxidant gas, the rotational speed confirmation means (40) for the oxidant pump (21), and the minimum speed at which the rotational speed of the oxidant pump (21) can be supported by an air bearing. When in the velocity region, the control means (40) is provided to increase the pressure of the oxidant gas via the pressure adjustment means (24) when the actual flow rate of the oxidant gas is higher than the target flow rate.

Description

  The present invention relates to a fuel cell system that generates power using a fuel gas and an oxidant gas.

The fuel cell system is a power generation system in which a fuel cell (stack) generates electricity electrochemically using fuel gas from a fuel gas supply source and oxidant gas from an oxidant gas supply source. Usually, air is used as the oxidant gas, and air as the oxidant gas is pumped to the fuel cell by the compressor.
In Patent Document 1, the controller calculates the target rotational speed of the compressor that pumps air to the fuel cell based on the accelerator opening, the vehicle speed, and the air flow rate of the fuel cell vehicle, and controls the rotational speed of the compressor. The amount of air supplied to the battery is controlled. For example, if the detected flow rate value detected by the flow rate sensor is within the normal range calculated based on the operating state of the fuel cell, feedback control of the air flow rate is performed using the detected flow rate value, and the detected flow rate value is within the normal range. When deviating outside, feedforward control of the air flow rate (compressor rotation speed) is performed.

JP 2010-241384 A

  By the way, a compressor has a turbo type air pump that is supported by an air bearing. However, in the case of an air bearing, there is a case where a target flow rate of air cannot be supplied to the fuel cell only by controlling the rotational speed. Specifically, when the desired air flow rate is supplied by performing feedback control of the rotational speed using the air flow rate detection value, the rotational speed command value is near the minimum rotational speed necessary for the shaft levitation of the air bearing. In this case, a desired air flow rate cannot be supplied only by controlling the rotation speed. By the way, it was found that when the rotation speed command value of the air pump stuck to the lower limit due to flow sensor error and variations in intake pressure / temperature, the flow rate would increase significantly due to the characteristics of the air pump ( (See FIG. 4).

In particular, in a system in which a device (such as a humidifier bypass valve) that changes the degree of pressure loss (hereinafter referred to as “pressure loss”) is installed between the air pump and the fuel cell, it can be seen that the above phenomenon becomes more prominent. It was.
Therefore, an object of the present invention is to provide a fuel cell system that can solve such a problem and can appropriately supply a target flow rate.

  (1) In the present invention in which the above-described problems have been solved, a fuel cell that is supplied with fuel gas and oxidant gas to generate power, an oxidant gas supply path to the fuel cell, and a rotary shaft that is supported by an air bearing. A turbo-type oxidant pump that takes in and feeds oxidant gas by rotational movement, an actual flow rate detecting means for the oxidant gas, a pressure adjusting means for the oxidant gas, and a rotational speed confirmation means for the oxidant pump. When the rotational speed of the oxidant pump is in the minimum rotational speed region where the shaft support by the air bearing is possible, when the actual flow rate of the oxidant gas is higher than the target flow rate, And a control means for increasing the pressure of the oxidant gas.

  According to this configuration, when the actual flow rate of the oxidant gas is larger than the target flow rate, the pressure of the oxidant gas is increased and the actual flow rate by the air pump is adjusted.

  (2) Further, in the present invention, the control means sets a target flow rate and a target pressure from a required current value to the fuel cell, and when the actual flow rate is larger than the target flow rate, a first predetermined value is set as the target pressure. Is added to set a new target pressure.

  According to this configuration, when the actual flow rate is higher than the target flow rate, the target pressure is increased (the oxidant pressure is increased), thereby adjusting the actual flow rate by the oxidant pump.

  (3) Moreover, in this invention, the humidifier arrange | positioned between an oxidizing agent pump and a fuel cell, the humidifier bypass path which bypasses a humidifier, and the oxidizing agent flow of a humidifier and a humidifier bypass path And an oxidant flow adjusting means (bypass valve or pre-humidifier pre-adjusting valve) for adjusting the ratio of the oxidant, and the control means sets the target pressure according to the adjustment ratio of the oxidant flow adjusting means. This is a fuel cell system.

  According to this configuration, even when the oxidant gas having the same flow rate is supplied to the fuel cell, the pressure loss (pressure loss) between the oxidant pump and the fuel cell differs depending on the adjustment ratio of the flow to the humidifier bypass passage. Even in this case, the target pressure is set according to the adjustment ratio.

  (4) In the present invention, the oxidant flow pressure loss value is obtained based on the relationship between the adjustment ratio of the oxidant flow adjusting means, the target flow rate, and the oxidant flow pressure loss, and the target pressure and the pressure loss value are calculated. When the total value is smaller than the predetermined value, the fuel cell system is characterized in that a new target pressure is set by adding the second predetermined value to the target pressure.

  According to this configuration, for example, control is performed as in steps S22 to S28 of the second embodiment described later, and the flow rate of the oxidant pump can be controlled more appropriately.

  (5) Further, in the present invention, when the oxidant flow adjusting means is a flow rate adjusting valve disposed in the bypass passage, and the control means sets the opening degree of the flow rate adjusting valve to be larger than the predetermined opening degree. Is characterized in that a new target pressure is set by previously adding a predetermined value to the target pressure.

  According to this configuration, since the opening degree of the flow rate adjustment valve is increased, the pressure loss between the oxidant pump and the fuel cell is reduced, and the flow rate of the oxidant gas tends to increase. For this reason, a predetermined value is added to the target pressure to increase the target pressure, thereby suppressing an increase in the flow rate of the oxidant gas.

  (6) Further, in the present invention, a fuel cell that is supplied with fuel gas and oxidant gas to generate power, an oxidant supply path through which the oxidant gas supplied to the fuel cell flows, and exhausted from the fuel cell An oxidant discharge path through which the oxidant off-gas flows, a rotary oxidant pump that takes in and sends the oxidant gas, an actual flow rate detecting means for detecting an actual flow rate of the oxidant gas, and a rotation of the oxidant pump Rotational speed confirmation means for confirming the speed, a back pressure valve arranged in the oxidant discharge passage for adjusting the pressure of the oxidant gas supplied to the cathode of the fuel cell, and the opening of the back pressure valve in the opening direction After the control, when the actual flow rate is higher than the target flow rate even when the rotation speed of the oxidant pump is reduced to the minimum rotation speed region, the opening degree of the back pressure valve is controlled in the closing direction and the opening direction. With a smaller opening Characterized in that it comprises a control means for controlling to reduction.

  According to this configuration, if the actual flow rate is higher than the target flow rate even if the rotational speed of the oxidant pump decreases to the minimum rotational speed range after controlling the opening of the back pressure valve in the opening direction, the back pressure valve The oxidant gas pressure rises and the actual flow rate becomes the target flow rate by controlling the opening of the valve to close and changing the back pressure valve opening to a smaller opening than when opening the valve. Can be reduced to

  (7) Moreover, in this invention, it is arrange | positioned at the said oxidant supply path, It is provided with the pressure detection means which detects the pressure of the oxidant gas supplied to the said cathode, The said control means is the said pressure to predetermined value. When it rises, the opening control of the back pressure valve is terminated.

  According to this configuration, the control means appropriately determines the end timing of the back pressure valve opening control by determining the end of the back pressure valve opening control based on the detected value (actual value) of the pressure of the oxidant gas. Can be controlled.

  (8) Further, in the present invention, when the output of the fuel cell is set to a predetermined low output state, the control means executes an opening degree control of the back pressure valve.

  According to this configuration, for example, in the vehicle (automobile) equipped with the fuel cell system, the control means opens the back pressure valve even when the vehicle decelerates and shifts to the idling state (predetermined low output state). By controlling the degree, it becomes possible to control the actual flow rate of the oxidant gas to the target flow rate.

  (9) Further, in the present invention, the control means executes the opening control of the back pressure valve when the output of the fuel cell is maintained in a predetermined low output state.

  According to this configuration, for example, in a vehicle (automobile) equipped with a fuel cell system, even when the vehicle is in an idling state (predetermined low output state), the actual flow rate of the oxidant gas cannot be reduced to the target flow rate. The actual flow rate can be lowered to the target flow rate by controlling the opening of the back pressure valve.

  ADVANTAGE OF THE INVENTION According to this invention, the fuel cell system etc. which can supply the target flow volume appropriately can be provided.

It is a figure which shows the structure of the fuel cell system which concerns on embodiment (1st Embodiment, 2nd Embodiment) of this invention. It is a flowchart of control concerning a 1st embodiment of the present invention. It is a flowchart of control concerning a 2nd embodiment of the present invention. It is a figure which shows the characteristic of an air pump, a horizontal axis is suction | inhalation volume flow volume, and a vertical axis | shaft is a pressure ratio. It is a flowchart of control concerning a 3rd embodiment of the present invention. It is a time chart in the control which concerns on 3rd Embodiment of this invention.

<< First Embodiment >>
Next, an embodiment (embodiment) for carrying out the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 is a diagram schematically showing an overall configuration of a fuel cell system 1 according to an embodiment of the present invention. In addition, this fuel cell system shall be mounted as a power supply in the fuel cell vehicle which drive | works with an electric motor.

  As shown in FIG. 1, a fuel cell system 1 includes a fuel cell 10, an air supply system 20 that supplies and exhausts air (air) as an oxidant gas to the fuel cell, and a fuel gas to the fuel cell 10. As a hydrogen supply system 30 for supplying and exhausting hydrogen, a control device 40 for controlling the fuel cell system 1, and the like.

  Among these, the fuel cell 10 is a well-known power generation device that includes an anode electrode (hydrogen electrode) 11 and a cathode electrode (air electrode) 12, and generates electricity electrochemically using hydrogen and air supplied to each. is there.

  The air supply system 20 includes an air pump 21, a humidifier 22, a humidifier bypass valve 23, and a back pressure valve 24 as main components. Furthermore, the air supply system 20 includes an air supply pipe 20 a that connects the air pump 21 and the inlet side of the cathode electrode 12 of the fuel cell 10 via a humidifier 22, and a bypass pipe 20 b that bypasses the humidifier 22. And an air discharge pipe 20c for discharging the air-off gas discharged from the outlet side of the cathode electrode 12 of the fuel cell 10 through the humidifier 20. The bypass pipe 20b includes a humidifier bypass valve 23. Since these components are generally used, description thereof is omitted.

The air pump 21 is a turbo type that is pivotally supported by the air bearing described in the background art, and has a function of taking in and sending out air by a rotational motion. This air pump 21 has a characteristic that a desired air flow rate cannot be obtained when the rotational speed command value is in the vicinity of the minimum rotational speed (minimum rotational speed region) necessary for the air bearing shaft to float (the minimum rotational speed region). (See FIG. 4).
Incidentally, the control device 40 confirms the rotational speed of the air pump 21 based on the rotational speed command value generated by itself, but it is confirmed by this rotational speed sensor by providing a rotational speed sensor such as a Hall element. You may make it do. A technique for controlling rotation without a sensor is generally known. Further, the humidifier bypass valve 23 is used as the “oxidant flow adjusting means”, but instead of or in addition to the humidifier bypass valve 23, a valve is provided immediately before the inlet of the humidifier 22 or immediately after the outlet. It may be “oxidant flow adjusting means”.

  The hydrogen supply system 30 includes a hydrogen supply system 31 as a main configuration. Further, the hydrogen supply system 30 includes a hydrogen supply pipe 30a that supplies hydrogen to the anode electrode 11 of the fuel cell 10, a hydrogen discharge pipe 30b that exhausts hydrogen off-gas from the anode electrode 11 of the fuel cell 10, and a hydrogen discharge pipe 30b. And a hydrogen return pipe 30c that branches from the pipe and returns to the hydrogen supply pipe. Incidentally, the hydrogen supply system 31 is provided with a hydrogen storage container (not shown) that stores hydrogen at an ultrahigh pressure of 30 MPa or 70 MPa. However, the hydrogen supply system 31 reforms liquid raw fuel such as methanol to generate hydrogen. You may provide the reformer which produces | generates.

  In FIG. 1, descriptions of an ejector, a purge valve, and the like are omitted. Since these components in the hydrogen supply system 30 are generally used, the description thereof is omitted.

  The control device 40 includes a central processing unit (CPU), a random access memory (RAM), a read only memory (ROM), various interfaces, and the like. The control device 40 is connected to the atmospheric pressure sensor Pa through various interfaces, and is connected to an intake air temperature sensor T, a flow rate sensor Q, and a pressure sensor Pb disposed in the air supply system 20. The detected value is input. The control device 40 is also connected to another control device (not shown) that determines a required current value (hereinafter referred to as “FC required current”) for the fuel cell 10 so that the FC required current is input. Incidentally, the FC required current is roughly the sum of the current value obtained in proportion to the amount of depression of the throttle pedal and the current value obtained in proportion to the operating amount of the auxiliary machine or the like.

  The control device 40 is connected to the air pump 21 (the drive circuit thereof), the humidifier bypass valve 23 (the drive circuit thereof), and the back pressure valve 24 (the drive circuit thereof) via various interfaces. Is generated and transmitted, and an opening degree command value is generated and transmitted to the humidifier bypass valve 23 and the back pressure valve 24. Incidentally, when the rotational speed command value increases, the rotational speed of the air pump 21 increases and the air flow rate supplied to the cathode electrode 12 of the fuel cell 10 increases (the flow rate detected by the flow sensor Q increases). In addition, if the opening degree of the humidifier bypass valve 23 is increased, the flow rate of air flowing through the humidifier 22 is decreased (the flow rate of air supplied to the cathode electrode 12 is not increased through the humidifier 22). Further, when the opening degree of the back pressure valve 24 is increased, the pressure of the cathode electrode 12 is decreased (the pressure detected by the pressure sensor Pb is decreased).

  The control device 40 in the present embodiment actively controls the amount of air supplied to the air supply system 20 by controlling the rotational speed of the air pump 21, but for the hydrogen supply system 30, The amount of hydrogen is not specifically controlled. It is assumed that the hydrogen supply amount from the hydrogen supply system 31 through a regulator (not shown) increases as the hydrogen consumption amount at the anode 11 increases (passively).

  The operation of the fuel cell system 1 according to the first embodiment having the system configuration described above will be described with reference to the control flowchart of FIG. The control of the humidifier bypass valve 23 will be described in the control flow of FIG. 3 to be described later.

First, based on the amount of depression of the throttle pedal and the load of the air conditioner (amount of operation of the auxiliary machine, etc.) A required power generation current (FC required current) is set, and the FC required current is transmitted to the control device 40. The control device 40 calculates a target air flow rate to be supplied to the fuel cell 10 from the FC required current with reference to a table or map stored in advance (step S10). Similarly, the target air pressure is calculated from the FC required current with reference to a table or a map (step S20).
Incidentally, the target air pressure is assumed to be at the inlet of the cathode electrode 12 (position of the pressure sensor Pb).

  Then, the back pressure valve 24 is feedback-controlled (F / B control) to adjust the opening of the back pressure valve 24 so that the value of the air pressure detected by the pressure sensor Pb becomes the target air pressure calculated in step S20 ( Step S30). Further, the rotational speed of the air pump 21 is hoodback-controlled so that the value of the air flow detected by the flow sensor Q becomes the target air flow calculated in step S10 (step S40). That is, the control device 40 sets (generates) a rotation speed command value and an opening command value based on the feedback control, and controls the air pump 21 and the back pressure valve 24. It is assumed that the air flow rate is corrected by the air temperature detected by the intake air temperature sensor T and the air pressure (atmospheric pressure) detected by the atmospheric pressure sensor Pa.

  Incidentally, as described above, the air pump 21 of the present embodiment is pivotally supported by the air bearing, and the rotational speed of the air pump 21 is set to a value higher than the minimum rotational speed (lower limit) necessary for the shaft lifting of the air bearing. Has been. In other words, when the amount of depression of the throttle pedal and the amount of operation of the auxiliary machine is small, or when the discharge from the high voltage battery is mainly performed, the power generation by the fuel cell 10 is not required, so the rotational speed of the air pump 21 is the lower limit. However, the rotational speed is still set to be slightly higher than the lower limit. However, due to errors in the flow rate sensor Q and the pressure sensor Pb, and due to variations in intake pressure (intake air pressure) and intake air temperature (intake air temperature) (depending on weather conditions and environment), the rotational speed of the air pump 21 reaches the lower limit. It may stick. At such a lower limit of rotation speed, there has been a problem that the air flow rate cannot be appropriately controlled, such as an unintended increase in the air flow rate (“the actual flow rate does not achieve the target flow rate”).

  Therefore, in the first embodiment, it is determined whether or not the air pump rotational speed is at the minimum rotational speed (lower limit) of the air pump 21 (step S50). If it is not at the lower limit, the processing is returned to the original, and the processing from step S10 is repeated (Return). Note that the lower limit is appropriately set by experiment, simulation, or the like.

  If the air pump rotational speed is at the lower limit (step S50 → YES), it is determined whether the air flow rate (actual value)> the target air flow rate (step S60). This is because, when the air pump rotational speed is at the lower limit, the air flow rate may increase significantly due to the characteristics of the air pump 21 supported by the air bearing (“the actual flow rate is higher than the target flow rate”). ). Incidentally, as described above, the control device 40 confirms the rotational speed of the air pump 21 based on the rotational speed command value generated by itself.

If the air flow rate is not greater than the target air flow rate (step S60 → NO), this can be said to be normal, and the processing is returned to the original, and the processing from step S10 is repeated (Return). On the other hand, if air flow rate> target air flow rate (step S60 → YES), the controller 40 adds the first predetermined value (first predetermined value ≧ 0) to the target air pressure set in step S20. A new target air pressure is set (step S70). Then, the opening of the back pressure valve 24 is adjusted in the closing direction so that the value of the air pressure becomes the target air pressure (step S80). That is, the control apparatus 40 adjusts in the direction which suppresses the air flow which is flowing excessively, and controls to the direction which suppresses the air flow. The control at this time may be a feed forward control, a feedback control or a control that takes both into consideration, but the feed forward control has a characteristic of quick response. The first predetermined value is a value set by experiment, simulation, or the like. However, even if the first predetermined value is a fixed value, the fluctuation varies based on a deviation between the air flow rate and the target air flow rate. It may be a value.
After the process of step S80, the process proceeds to step S60 and the process is continued.

  According to the first embodiment, when the rotational speed of the air pump 21 reaches the lower limit (S50 → YES), and when the air flow rate> the target air flow rate (step S60 → YES), the air flow rate is excessive. Has become out of control. Therefore, the control device 40 increases the target air pressure (step S70) and adjusts the back pressure valve 24 in the closing direction (step S80). Thus, an appropriate air flow rate can be ensured.

  That is, in a system that employs a turbo-type air pump that is pivotally supported by an air bearing, such as the air pump 21 of the present embodiment, the rotational speed command value of the air pump 21 is in the vicinity of the minimum number of revolutions necessary for the air bearing shaft to float. Even in the case (minimum rotation speed region), a desired air flow rate can be supplied by adjusting the pressure command value (the opening degree of the back pressure valve 24). For this reason, it is possible to prevent excessive air supply to the fuel cell 10 (cathode electrode 12), and it is possible to perform efficient power generation while preventing overdrying of the electrolytic membrane, thereby greatly improving the reliability of the system. . Supplementally, when the supply amount of air increases, the air tends to dry. This causes the electrolyte membrane of the fuel cell 10 to dry, and the IV characteristics (current / voltage specification) of the fuel cell 10 deteriorate, that is, the fuel cell 1. However, according to the fuel cell system 1 of the present embodiment, this is suppressed. Further, a decrease in system efficiency due to prevention of useless air supply is suppressed.

  Incidentally, since the region where the rotational speed of the air pump 21 is low (low rotational speed region) is a region where the amount of power generated by the fuel cell 10 is small, naturally, the amount of water generated by the electrochemical reaction is also small. For this reason, it can be said that the electrolyte membrane is in a state where it is easy to dry, and supplying excessive air in such a situation tends to cause overdrying of the electrolyte membrane (and thus power generation efficiency and deterioration of the electrolyte membrane). According to this embodiment, this is suppressed.

<< Second Embodiment >>
Next, the second embodiment will be described according to the control flowchart of FIG. 3 with reference to FIG. 1 as appropriate. In addition, 2nd Embodiment performs the control which considered the opening degree of the humidifier bypass valve 23 in the fuel cell system of the system configuration | structure of FIG. For this reason, in the control flowchart of FIG. 3, the same step numbers as those in FIG. 2 are assigned to portions common to the first embodiment, and description thereof will be omitted as appropriate.

  As shown in FIG. 3, as in the first embodiment, the control device 40 performs step S10 (target air flow rate calculation) and step S20 (target air pressure calculation). Next, the opening degree of the humidifier bypass valve 23 (humidifier bypass valve opening degree) is calculated from the FC required current (step S22). Next, in the second embodiment, the pressure loss (humidifier pressure loss) in the humidifier 22 is calculated from the target air flow rate and the opening degree of the humidifier bypass valve 23 (step S24).

  FIG. 3 conceptually shows a map of the relationship between the target air flow rate, the humidifier pressure loss, and the humidifier bypass valve opening. As shown in this map, the target air flow rate and the humidifier pressure loss are As the target air flow rate increases, the humidifier pressure loss also increases. In addition, even when the target air flow rate is the same, there is a relationship in which the humidifier pressure loss decreases as the humidifier bypass valve opening increases. This map is “the relationship between the adjustment ratio of the oxidant flow adjusting means, the target flow rate, and the oxidant flow pressure loss”. By the way, the map is an example, and it may be a function, a table, or others.

  The control device 40 determines whether the value obtained by adding the target air pressure and the humidifier pressure loss is smaller than the predetermined value, that is, whether the target air pressure + humidifier pressure loss <the predetermined value (step S26). The default value is a value set by experiment or simulation.

  If target air pressure + humidifier pressure loss <predetermined value (step S26 → YES), a second predetermined value is added to the target air pressure to calculate a new target air pressure. Then, the process proceeds to step S30. Moreover, also when step S26 is NO, it transfers to step S30. The second predetermined value is a value larger than 0 (second predetermined value> 0), and is set by experiment or simulation. Since step S30 and subsequent steps are the same as those in the first embodiment, description thereof is omitted.

  In the fuel cell system 1 in which a device for changing air pressure loss (here, the humidifier bypass valve 23) is installed between the air pump 21 and the fuel cell 10, the above-described event, that is, the lower rotational speed range of the air pump 21. The increase in the air flow rate becomes more remarkable. Supplementally, when the opening degree of the humidifier bypass valve 23 changes, the pressure loss from the air pump 21 to the fuel cell 10 changes. Usually, the air supply is controlled so that the pressure (detected by the pressure gauge Pb) at the inlet of the fuel cell 10 (inlet of the cathode electrode 12) becomes predetermined. However, when the opening degree of the humidifier bypass valve 23 changes, the outlet pressure (air pump compression ratio) of the air pump 21 changes, and the vertical axis of the “variation” region (see FIG. 4) changes greatly. For this reason, the above-mentioned phenomenon becomes remarkable.

  However, in the second embodiment, the humidifier pressure loss is calculated (step S24), and the control taking this pressure loss into account is performed (steps S26 and S28), and the target air pressure is set to a new target air taking into account the humidifier pressure loss. Use pressure. Since the back pressure valve 24 is controlled in step S30 by this new target air pressure, an increase (unintentional increase) in the air flow rate is suppressed, and an appropriate air flow rate is ensured.

  Therefore, according to the second embodiment, the fuel cell system 1 can be appropriately operated with an appropriate air flow rate as in the first embodiment, and the air pump 21 and the anode 12 can be operated. Since the presence of a device that changes the air pressure loss is taken into account, the fuel cell system 1 can be operated more appropriately than in the first embodiment.

≪Others≫
In the second embodiment, the map in FIG. 3 is referred to in step S24. For example, a flow rate control in which a device (oxidant flow adjustment unit) for controlling the flow distribution of the adjustment unit is installed in the bypass pipe 20b. In the case of the valve (humidifier bypass valve 23), when the opening degree of the flow control valve (humidifier bypass valve 23) is larger than the predetermined opening degree and the compression ratio of the air pump 21 is expected to be low (flow rate adjustment) When the opening degree of the valve is set larger than the predetermined opening degree), the control means 40 increases the target pressure in advance, that is, adds a predetermined value (third predetermined value) to the target pressure in advance. A target flow rate by the air pump 21 may be achieved by setting an appropriate target pressure. Each predetermined value is a value that is set as appropriate in order to achieve the purpose of supplying an appropriate air flow rate by adjusting the actual flow rate to the target flow rate (in order to suppress an excessive flow rate). .

«Third embodiment»
Next, a third embodiment will be described with reference to FIGS. 5 and 6 (FIG. 1 as appropriate). In the third embodiment, for example, in a fuel cell vehicle in which the fuel cell system having the system configuration shown in FIG. 1 is mounted on a vehicle (four-wheeled vehicle, two-wheeled vehicle, etc.), the fuel cell vehicle decelerates from a running state, In the idling state in which the minimum output of the battery 10 is maintained (when the generated power of the fuel cell 10 is set to a predetermined low output state), the opening degree of the back pressure valve 24 is controlled in the opening direction. In other words, when the opening degree of the back pressure valve 24 is decelerated from the traveling state and shifted to the idling state, the back pressure valve 24 is changed more greatly than when it is controlled in the opening direction during normal traveling. In addition, the same step number as FIG. 2 is attached | subjected about the part which is common in 1st Embodiment, and description is abbreviate | omitted suitably.

  As shown in FIG. 5, when it is determined that the air flow rate (actual flow rate) is higher than the target air flow rate (S60 → Yes), the control device 40 adjusts the opening of the back pressure valve 24 to be small (step S90). ). That is, when the vehicle is decelerated from the running state and shifted to the idling state, the opening degree of the back pressure valve 24 is controlled to change smaller than when it is largely controlled in the opening direction.

  And the control apparatus 40 determines whether an air pressure is more than predetermined pressure (step S100). The predetermined pressure is a threshold value for determining whether or not to adjust the opening degree by the back pressure valve 24. When it is determined that the air pressure is not equal to or higher than the predetermined pressure (S100 → No), the control device 40 returns to step S60, and when it is determined that the air pressure is equal to or higher than the predetermined pressure (S100 → Yes), The opening degree adjustment of the pressure valve 14 is finished (step S110).

  Further, with reference to FIG. 6, when shifting to a predetermined low output state (for example, idling state), the opening degree of the back pressure valve 24 is largely controlled and the rotational speed of the air pump 21 is decreased (time t0). -T1). In this case, the opening degree of the back pressure valve 24 is controlled to be greatly changed by the process of step S30 in FIG. 5, and the rotation speed of the air pump 21 is controlled to be low by the process of step S40 in FIG. Air pressure drops significantly.

  When the opening degree of the back pressure valve 24 is controlled to change greatly at time t1, the rotational speed of the air pump 21 reaches the lower limit rotational speed, and the rotational speed of the air pump 21 cannot be further reduced (S50 → Yes). ) When the air flow rate (actual flow rate, see solid line) still does not reach the target air flow rate (see broken line) (S60 → Yes), that is, it is detected that the air flow rate (actual flow rate) is excessive, and the air pressure In order to increase the air pressure and decrease the air flow rate (actual flow rate), the opening of the back pressure valve 24 is changed small in the closing direction (S90). At this time, the air pressure increases by changing the opening of the back pressure valve 24 in the closing direction. Thus, the air flow rate (actual flow rate) gradually decreases by changing the opening of the back pressure valve 24 to a small value.

  At time t2, when the air pressure reaches a predetermined pressure by adjusting the opening of the back pressure valve 24 (S100 → Yes), the opening control of the back pressure valve 24 is ended (S110). At this time, the air flow rate (actual flow rate) becomes the target air flow rate.

  Therefore, according to the third embodiment, when the traveling state is shifted to the idling state, the opening speed of the back pressure valve 24 is largely changed in the opening direction, and then the rotational speed of the air pump 21 is set to the lower limit rotational speed (minimum rotational speed). When the air flow rate (actual flow rate) is still larger than the target air flow rate, the air pressure (oxidant gas pressure) can be reduced by changing the opening of the back pressure valve 24 in the closing direction. ) And the air flow rate (actual flow rate) can be reduced to the target flow rate. By adjusting the opening degree of the back pressure valve 24 in this way, an increase (unintended increase) in the air flow rate is suppressed, and an appropriate air flow rate is ensured.

  Further, according to the third embodiment, when the air pressure rises to a predetermined pressure, the opening control of the back pressure valve 24 can be appropriately performed by ending the opening control of the back pressure valve 24.

  Moreover, according to the third embodiment, by applying to the case where the output of the fuel cell 10 is set to a predetermined low output state (idling state), an increase in the air flow rate can be suppressed and an appropriate air flow rate can be secured. .

  In the third embodiment, the case where the vehicle decelerates and shifts to the idling state is described as an example of the situation in which the opening degree control of the back pressure valve 24 is executed. However, the third embodiment is applied only in such a situation. Instead, during the idling state, for example, when the power supply to the air pump 21 fluctuates temporarily as the load on the entire vehicle fluctuates, such as when the use of the heater for heating is started. The present invention may be applied even when the actual flow rate fluctuates slightly and as a result, the actual flow rate cannot be lowered to the target air flow rate.

DESCRIPTION OF SYMBOLS 1 Fuel cell system 10 Fuel cell 11 Anode electrode 12 Cathode electrode 20 Air supply system 20a Air supply piping (oxidant supply channel)
20b Bypass piping (humidifier bypass)
20c Air discharge pipe (oxidant discharge path)
21 Air pump (oxidizer pump)
22 Humidifier 23 Humidifier bypass valve (oxidant flow adjustment means, flow rate adjustment valve)
24 Back pressure valve (pressure adjusting means)
30 Hydrogen supply system 31 Hydrogen supply system 40 Control device (control means, rotation speed confirmation means)
Pb pressure sensor (pressure detection means)
Q Actual flow rate detection means (flow rate sensor)

Claims (9)

A fuel cell that is supplied with fuel gas and oxidant gas to generate electricity;
An oxidant supply path to the fuel cell;
A turbo-type oxidant pump whose rotary shaft is pivotally supported by an air bearing and takes in an oxidant gas by rotational movement;
Means for detecting the actual flow rate of the oxidant gas;
Pressure adjusting means for the oxidant gas;
Means for confirming the rotational speed of the oxidant pump;
When the rotational speed of the oxidant pump is in a minimum rotational speed region where the shaft support by the air bearing is possible, when the actual flow rate of the oxidant gas is higher than a target flow rate, the oxidation is performed via the pressure adjusting means. Control means for increasing the pressure of the agent gas;
A fuel cell system comprising: The control means includes
Set the target flow rate and target pressure from the required current value to the fuel cell,
2. The fuel cell system according to claim 1, wherein when the actual flow rate is higher than the target flow rate, a new target pressure is set by adding a first predetermined value to the target pressure. A humidifier disposed between the oxidant pump and the fuel cell;
A humidifier bypass path for bypassing the humidifier;
An oxidant flow adjusting means for adjusting a ratio of an oxidant gas flow between the humidifier and the humidifier bypass path;
The fuel cell system according to claim 2, wherein the control unit sets the target pressure in accordance with an adjustment ratio of the oxidant flow adjusting unit. Based on the adjustment ratio of the oxidant flow adjusting means and the relationship between the target flow rate and the oxidant flow pressure loss, an oxidant flow pressure loss value is obtained,
When the total value of the target pressure and the oxidant flow pressure loss value is smaller than a predetermined value,
4. The fuel cell system according to claim 3, wherein a new target pressure is set by adding a second predetermined value to the target pressure. The oxidant flow adjusting means is a flow rate adjusting valve disposed in the humidifier bypass passage,
The control means
When the opening of the flow rate adjustment valve is set larger than a predetermined opening,
The fuel cell system according to claim 3 or 4, wherein a new target pressure is set by adding a predetermined value to the target pressure in advance. A fuel cell that is supplied with fuel gas and oxidant gas to generate electricity;
An oxidant supply path through which an oxidant gas supplied to the fuel cell flows;
An oxidant discharge passage through which an oxidant off-gas discharged from the fuel cell flows;
A rotary oxidant pump that takes in and delivers oxidant gas;
An actual flow rate detecting means for detecting an actual flow rate of the oxidant gas;
Rotation speed confirmation means for confirming the rotation speed of the oxidant pump;
A back pressure valve that is disposed in the oxidant discharge passage and adjusts the pressure of the oxidant gas supplied to the cathode of the fuel cell;
After controlling the opening degree of the back pressure valve in the opening direction, if the actual flow rate is higher than the target flow rate even if the rotation speed of the oxidant pump decreases to the minimum rotation speed range, the opening degree of the back pressure valve is closed. Control means for controlling the direction to change with a smaller opening than when controlling in the opening direction;
A fuel cell system comprising: A pressure detecting means disposed in the oxidant supply path for detecting the pressure of the oxidant gas supplied to the cathode;
The fuel cell system according to claim 6, wherein the control means ends the opening control of the back pressure valve when the pressure rises to a predetermined pressure.   8. The fuel cell system according to claim 6, wherein when the output of the fuel cell is set to a predetermined low output state, the control means performs opening control of the back pressure valve. 9.   8. The fuel cell system according to claim 6, wherein when the output of the fuel cell is maintained in a predetermined low output state, the control unit performs opening control of the back pressure valve. 9. .

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